Hydrodynamic simulation of rough-walled submarine far field turbulent wakes.

Abstract: A study of far-field turbulent wakes from a generic fully appended DARPA SUBOFF submarine model using computational methods via Reynolds-Averaged Navier-Stokes (RANS) simulation at Reynolds number of ReL = 1.0x10^6 was conducted. Such a study is known to be challenging both experimentally and numerically due to its long development length required and the broad range of spatial scales. Here, the investigation examines both smooth and rough hull surfaces, with the rough-wall case having an equivalent sand-grain roughness of ks = 0.3 mm, simulating somewhere between heavy slime and light calcareous tubeworm fouling. A unique aspect of this study is the very long domain length, extending up to 80 submarine diameters downstream of the model, in order to sufficiently analyse wake formation and its associated turbulence statistics. Initial results reveal that the mean streamwise velocity and turbulent kinetic energy from the smooth wall case approach self-similarity at 75 submarine diameters. For the rough wall case, however, the flow is unable to achieve self-similarity at 75 submarine diameters, and it would require a longer downstream distance to reach such flow behaviour. Keywords: RANS, DARPA Sub-off submarine, Far-field flow, Turbulent wakes.